This application pertains to the art of machine tooling and more particularly to the art of radius grinding of various workpieces such as lathe tools and the like.
The invention may be particularly applicable to radius grinding of small parts such as lathe tools and will be described with particular reference thereto, although it will be appreciated that the invention has broader applications, including any machining step wherein pivotal manipulation of a workpiece is desired.
The machining of various parts has heretofore required grinding or other machining of the parts to form various radial machine surfaces, such as radiused edges, corners, and the like. Frequently, the machining of relatively small workpiecse requires adherence to very closer tolerances, such that, where a radial surface is called for, the machining of such surface must be carried out with extreme care, so as to adhere to the prescribed tolerances. Even small errors in positioning of the workpiece during machining may lead to a final product which is outside the prescribed tolerances and must, therefore, be discarded. Such errors may be extremely costly, especially with parts which have been subjected to multiple machining steps prior to the step where the error is made. Indeed, such errors are costly not only in terms of material costs, but in view of the extensive labor involved in the preparation of such parts.
In order to minimize the likelihood of error in preparing machine tools to specific tolerances, it has heretofore been common practice to utilize various fixtures, jibs, manipulators, vices, and other holding devices to precisly position the part during the machining process. Such positioning devices frequently incorporate and employ a vice or clamp-like mechanism to hold the workpiece firmly in place. Alternatively, such positioning devices may be in the form of "offhand" fixtures which provide a means of precisely positioning an individual workpiece without requiring tightening of a vice or other rigid clamping of the workpiece to the fixture. Fixtures of this type often employ a positioning block or straight edge which may be precisely adjusted. A workpiece may then be held against the preadjusted guide block or straight edge during machining. Such "offhand" positioning devices permit relatively rapid removal and replacement of one workpiece by another without the necessity of losening/tightening rigid clamping mechanisms and the like.
The machining of close-tolerance radial surfaces is frequently accomplished by positioning a workpiece in a rotationally adjustable fixture, such that the workpiece may be pivoted about a specific point. The workpiece is then placed in contact with a grinding wheel or other tooling surface and subsequently pivoted about a center point so as to result in grinding or machining of the workpiece to form the desired radius thereon. However, in the prior art devices, the centerpoint around which the workpiece is pivoted necessarily lies within the confines of the fixture itself. Since the workpiece will normally be positioned so as to extend over or beyond the edge of a given fixture in order to provide for contact of the workpiece with the machining tool, mechanisms which pivot about an internally located pivot point may be less than optimal when a close tolerance radius is required at the extreme tip of the workpiece.
Thus, there exists a substantial need in the art for a fixture or other device which provides a means of pivoting a workpiece about a point which lies beyond the confines of the fixture device itself.